Termination device with removable center conductor



Sept. 11, 1962 J. R. BIRD ETAL TERMINATION DEVICE WITH REMOVABLE CENTERCONDUCTOR Original Filed Feb. 4, 1955 2 Sheets-Sheet 1 0 wwmm R5 E m N mE ww W50 w IEL A Sept. 11, 1962 .1. R. BIRD ETAL 3,054,074

TERMINATION DEVICE WITH REMOVABLE CENTER CONDUCTOR Original Filed Feb.4, 1953 2 h t 2 |NVENTOR5 JAMES P. B/PD HAQOLD E. 57'EVEN5 50M,5W,

HMMMM ATTORNEYS 3,054,074 Patented Sept. 11, 1962 j free 3,054,074TERMINATION DEVECE WITH REMOVABLE CENTER CONDUCTOR James R. Bird,Chagrin Falls, and Harold E. Stevens,

Lyndhurst, Ohio, assignors to Bird Electronic Corporation, Cleveland,Ohio, a corporation of Ohio Original application Feb. 4, 1953, Ser. No.335,118, new Patent No. 2,884,603, dated Apr. 28, 1959. Divided and thisapplication Mar. 11, 1959, Ser. No. 798,727 21 Claims. (Cl. 33322) Thisinvention relates to high frequency electrical devices and hasparticular reference to coaxial line components of the reflectionlesstermination type used either alone for attenuation or absorption of wavesignal energy or in conjunction with suitable detector, sampling, pickupor voltage dividing devices as a measuring instrument or the like.Reference is made to co-pending parent application for United Statespatent, Serial No. 335,118, filed February 4, 1953, now Patent2,884,603, of which this is a division.

The transmission, absorption and measuring of high frequency electricalenergy is more difificult in many respects than the correspondingtreatment or handling of low frequency or direct current electricalenergy because of capacitive and inductive effects, reflections andother phenomena. High frequency energy is satisfactorily transmitted oncoaxial lines and it is known that a coaxial transmission line can beterminated substantially reflectionlessiy by a device which incorporatescoaxial inner and outer conductors, one of which is tapered and one ofwhich is resistive, the tapered conductor desirably taking the form of atubular metal horn surrounding a cylindrical insulator of ceramic orlike material on which is deposited or otherwise formed a film ofcarbon, or equivalent, the latter constituting the inner conductor ofthe line termination. In such arrangement the smaller end of the outerhorn conductor makes direct electrical connection with resistive carbonfilm at one end of the inner conductor, thus completing the circuit.

Electrical energy fed into a line termination of the character mentionedis absorbed all along the resistive inner conductor, resulting inheating of the carbon film. At low energy levels the energy issatisfactorily dissipated into the atmosphere as by blowing air over theresistive film or by permitting air to circulate over the resistive filmthrough the action of convection currents. It has also been proposed toemploy a liquid dielectric coolant in the annular tapered dielectricspace which separates the inner and outer conductors of the terminationfor forced flow or convective circulation of such coolant through thedielectric space either axially of the device or transversely thereof.

By reason of the geometry of the reflectionless device, requiring closeproximity of the inner and outer conductors at one end of the device andwide separation thereof at the other end, and the need for substantiallyuniform heat absorption all along the length of the resistive conductor,servicing, checking and repairing such devices present numerousproblems. The present invention is therefore concerned primarily withand has for one of its principal objects the provision of a newapparatus for reflectionlessly terminating a coaxial transmission linewhich incorporates novel manufacturing, assembling and servicingadvantages. More particularly, the device combines inner and outercoaxial conductors arranged as a rcflectionless termination with theinner conductor axially withdrawable from and reinsertable into theouter conductor. As a refinement, the inner and outer conductors areseparated by an insulator and operative means is provided for stressingand deforming the insulator to grip the conductors to hold them againstaxial shifting relative to the insulator and to one another, theoperative means being actuatable to relieve the stress on the insulatorand the parts being proportioned and arranged for axial withdrawal ofthe inner conductor from and reinsertion of the same or a similar innerconductor into the outer conductor when the insulator is so relieved.

Another and more specialized object is to provide such a device havingan inner conductor withdrawable from and reinsertable into a coaxialouter conductor with which it forms a reflectionless termination inwhich the coaxial termination is contained in a housing from which it isremovable and reinsertable axially as a unit without disturbing therelative positions of the inner and outer conductors.

Cooling of the circulating coolant which has been heated by flowing overthe hot resistive conductor is effected preferably, though notnecessarily, in a zone wholly removed from the termination, this alsobeing an objective. The coolant may, for example, be passed through aheat exchanger separate from the termination and thereafter returned tothe resistor. The coolant thus com. pletes a closed circuit in which theflow may be induced by convection but preferably is accomplished bypowerdriven pump means which is more effective in obtaining the highflow rate desired to secure, in sectional area, preferably uniform'alongthe length of the resistive conductor and, in the case of a devicehaving a resistive center conductor of circular cross section,surrounding such resistive conductor..

Another object of the invention is to provide a combination whichcomprises a coaxial line component or termination of the charactermentioned in association with a casing or housing for holding a suitableliquid dielectric coolant, the line termination being immersed in theliquid dielectric coolant contained in the casing. In the arrangementpreferred as an embodiment of this aspect of the invention thecasing isincluded in a fluid coolant circuit which also includes a heat exchangerconnected by suitable conduits or tubes for the serial flow of coolantas by means of a power driven pump also included in the coolant circuit.In flowing through the casing the coolant absorbs heat by direct contactwith the resistive element of the coaxial line component or termination;in flowing through the heat exchanger the coolant gives up heat, say toa circulating refrigerant such as water passed through pipes or tubesimmersed in a body of the circulating liquid dielectric contained in theheat exchanger receptacle. This separation of the line terminationcasing from the heat exchanger receptacle and the forced serial flow ofcoolant therethrough is an objective of the invention.

In a specialized version of the apparatus wherein the coaxial device isin the form of a reflectionless termination and the liquid dielectriccoolant is contained in a casing which encloses or houses thetermination and wherein the coolant is forced to flow over a closedcircuit, the present invention also contemplates a further refinementwherein the flowing coolant is brought into the casing through anentrant tube, preferably in the bottom of the casing and is confined anddirected to flow from such entrant tube directly into the dielectricspace separating the inner and outer conductors of the termination, thisbeing an objective of the invention.

It is a further objective of the invention to provide a combination oftubular circular sectioned casing and contained termination or coaxialdevice wherein the latter is coaxial to the casing and acts as apartition or flow barrier controlling the movement of liquid dielectriccoolant through the casing. In the preferred embodiment contemplated thecoaxial termination device is axially withdrawable from and reinsertableinto the casing and has a tapered outer conductor having a portion ofmaximum cross sectional area or diameter intermediate its ends whichmaximum section portion engages or has substantially sealing relationwith the cylindrical casing wall by which it is surrounded to divide thecasing chamber and constrain the flowing dielectric coolant to flowthrough the interior of the termination.

Other objects and advantages pertain to certain novel combinations ofparts and features of construction, including capacitance compensationat the small end of the termination, the arrangement of the terminationon a vertical axis with provision for axial withdrawal of the innerconductor structure, provision for telescopic assembly of the severalcomponent parts of the termination device and casing with advantageouslocating and guiding relationships and positive securement of the innerconductor structure to resist shifting and turning in use. Such andstill other objectives and advantages are apparent in the followingdetailed description of a preferred embodiment of the invention, itsdescription being made in connection with the accompanying drawingsforming a part of the specification.

In the drawings:

FIGURE 1 is an elevational view, partly diagrammatic and with partsbroken away and removed, showing a high frequency electrical meterinstrument which incorporates a reflectionless termination for a coaxialtransmission line embodying the principles of the present invention;

FIG. 2 is a fragmentary elevational view, partly in section, partlydiagrammatic and with parts broken away and removed, showing the casingcontaining the line termination component of the device of FIG. 1, thisview being enlarged with respect to that figure;

FIG. 3 is a transverse sectional view, with parts removed, takensubstantially in the plane designated by the line indicated at 33 ofFIG. 2;

FIGS. 4 and 5 are fragmentary sectional views taken longitudinallythrough the upper and lower portions respectively of the reflectionlesstermination component and the casing for such component, these viewsbeing enlarged with respect to FIG. 2;

FIG. 6 is a sectional detail in the plane designated by the lineindicated at 6-6 of FIG. 4, being enlarged with respect to that figure;

FIG. 7 is a longitudinal sectional detail showing an expansible sectionof the center conductor and the manner in which an implement is insertedaxially into the movable element or expander of such section to turnsuch element in effecting expansion;

FIG. 8 is a transverse sectional detail taken substantially in the planedesignated by the line indicated at 8-8 of FIG. 5 and enlarged withrespect to that figure; and

FIG. 9 is an enlarged sectional detail, diagrammatic in character,showing the terminal contact band of thin brass soldered about thecopper plated end of the resistive inner conductor at the lower or smallend of the termination.

The high frequency electrical meter device illustrative of the presentinvention comprises a reflectionless termination T received in anelongated casing C, the latter preferably taking the form of acylindrical metal tube 1 of brass or steel, although other crosssectional shapes can be used. The top and bottom ends of the casing areclosed by circular metal plates 10 and 11, respectively, the latterbeing permanently secured in place as by peripheral welding 12. The topor cover disc 10 is peripherally grooved and held in place by clampingring 14. An interposed rubber O-ring effects a fluid tight seal betweenthe casing flange and the cover it).

At its upper end the body tube 1 of the casing C is connected to andsupported by a heat interchanger or receptacle R comprising a body 16closed at the bottom by a disc similar to the disc 11 of the casing C,and at the top by a cover 17 bolted to a flange 19 formed or welded inplace about the upper end of the body tube 16. The bottom of thereceptacle R rests on a pedestal or base 20 4 which also serves as asupport for an electrical motor 21 that in turn supports and drives acoolant circulating pump 8.

The connection between the casing C and the receptacle R at their upperends comprises aligned metal coupling tubes 22 welded into alignedopenings in the body tubes and attached together by flanged joint 23sealed by a suitable ring or gasket. At the bottom end of the casing Cconnection is made to the lower part of the receptacle R through thepump 8. The inlet of the pump is connected by a metal tube 24- to thebottom of the receptacle 16, a flanged joint 25 being interposed tofacilitate assembly and disassembly. The tangential outlet of the pump,indicated at 26, is connected by aligned tubes 27 and 28 to the lowerend of the casing C, a flanged joint 29 being provided between thetubes. A liquid coolant having suitable dielectric properties fills thecasing and receptacle for serial flow therethrough in a closed circuit.

In operating the device the motor 21 is energized to drive the pump 8,which forces the liquid dielectric coolant upwardly into the bottom ofthe casing C. As shown in FIG. 5, the tube 28 extends into the bottom ofthe casing through a circular opening 30 in the bottom closure 11. Inthe receptacle which constitutes a heat exchanger to cool the liquid theflow of the liquid dielectric coolant is generally downwardly, liquidcoolant entering the top of the receptacle from the casing C displacingliquid from the bottom of the receptacle and forcing the latter to flowout the bottom discharge tube 24 of the receptacle into the intake ofthe pump, thus completing the liquid coolant cycle.

As indicated in FIG. 1, the receptacle R is much larger than the casingC and has a volumetric capacity many times that of the casing to promotetempering and provide for adequate cooling of the circulating liquid.The cooling of the dielectric liquid occurs principally during itsdownward flow in the receptacle R, such cooling being effected by anysuitable arrangement familiar to the heat exchanger art, such as heattransfer by conduction through the metal walls of the body tube 16 anddissipation into the atmosphere by radiation and convection, the heattransfer, if desired, being a cooling medium such as cold water from aconventional pressurized water supply system that is circulated indirect heat exchange rel tion to the liquid dielectric in the receptacleR, the water being passed through a coil or coils 33 disposed within thereceptacle and having inlet and outlet tubes 34 and 35, respectively,projected through the top closure 17.

The inlet 34 is connected as to a city water supply system by suitableconduits and valves (not shown), one valve being an electricallyoperated or solenoid valve preferably of the water pilot type responsiveto a thermostatic switch immersed in the liquid dielectric coolant inthe receptacle R and carried as by a boss on the receptacle top. Theswitch is arranged to open the water or coolant supply valve when thetemperature of the liquid dielectric coolant becomes heated to apredetermined temperature, say about 35 centigrade in the case of thediphenyl, diphenyl oxide mixture mentioned, and to close the valve whenthe liquid dielectric coolant is cooled to a predetermined temperature,say about 30 centigrade when using such material, the electric valvethus automatically supplying the cold water or other refrigerant so asto maintain the circulating liquid dielectric coolant withinpredetermined temperature limits. The energization of the pump drivemotor 21 is governed manually to be turned on each time beforeelectrical energy is fed into the device or, preferably, the pump isoperated automatically to circulate the liquid dielectric coolantWhenever energy or power is fed into the termination T andsimultaneously with such feeding.

A further control refinement comprises a pair of series connectedthermostatic switches responsive to the temperature of the dielectriccoolant in the receptacle R. These switches act through suitable relaysor other controls to prevent operation of the equipment with which thepresent instrument is associated, say for example, a televisiontransmitter, when such temperature is objectionably high, say aboveabout 50 centigrade for the diphenyl, diphenyl-oxide mixture mentioned,and when such temperature is objectionably low or close to the freezingpoint of the liquid coolant, say below about 12 centigrade for suchmixture. Still another thermostatic switch immersed in the liquid in thereceptacle and responsive to the liquid temperature controls theenergization of an electrical immersion heater, not shown, which isregulated in this manner to keep the temperature of the liquid coolantabove the freezing point. The latter thermostatic switch may projectupwardly through a port in a boss in the receptacle top 17, the boss andthe upper end of the switch assembly being enclosed in a cover 38. Theswitches interlocking the signal generating equipment are mounted inother bosses under similar covers, not shown, on the top 17.

The termination T extends downwardly into the casing C through the topopening in the latter, in fact, being carried by the top 17 in suspendedrelation and inserted into the casing through such top opening inassembly. The general construction and geometry of the termination Tfollow well known principles enunciated, for example, in United StatesPatents 2,552,707, dated May 15, 1951, and 2,556,642, dated June 12,1951, and application for United States Patent Serial No. 72,782, filedJanuary 26, 1949. There are, however, certain improvements in thecombination of parts and refinements in the structure of the terminationthat are features and objectives of the present invention, as willappear.

The termination has an inner resistive conductor in the form of a carbonfilm 44 or equivalent, deposited or otherwise formed on the outercylindrical surface of a ceramic tube 41. Surrounding the innerresistive conductor in coaxial relation thereto is an outer taperedconductor 42 which may take the form of a metal horn spun or stampedfrom brass or similar thin metal. The horn is curved or shaped inaccordance with the known principles referred to above so as to providea characteristic impedance at any point or section which issubstantially equivalent to the resistance of that portion of theresistive inner conductor 40 which lies between the point or section ofreference and the small end of the termination where the inner and outerconductors are mechanically and electrically joined.

At its upper or large diameter end the tapered horn outer conductor 42is formed with an integral cylindrical extension or connector section 44received telescopically within a matched cylindrical socket openingthrough the bottom end of a body member 45 which is of circular sectionand may be in the form of a spinning or, as shown, a turning of brass orother metal. The conductive parts of the device are machined from brassstock, except as otherwise indicated or implied. The circular body 4'5has an external surface 46, here cylindrical, that is complemental toand has a freely sliding fit in the cylindrical body tube 1 of thecasing or, as shown, in cylindrical reinforcing band 47 previously pressfitted into the body tube of the casing to reinforce the walls of thelatter. The upper open end of the circular body 45 is formed with ashallow cylindrical socket 49 axially aligned with the socket thatreceives the connector 44. One end of a cylindrical relatively thinwalled metal connector tube 55 is received in the shallow socket 49 andextends upwardly therefrom through the upper portion of the casing incoaxial relation and through a central opening 51 in the top closure 10.The connector tube 5%, of brass or copper, is secured in the shallowsocket 49 as by soldering or brazing and additionally by a plurality ofradial set screws 52 threaded through the termination sealing ring 127comprising an element of a tubular guide for the flowing liquiddielectric coolant.

A ring 54 is formed on or welded at 55 against the underside of the topclosure 10 about the center opening that receives the connector tube 50.Radial set screws 56 are threaded through the ring 55 and are receivedthrough openings in the connector tube so as to bear radially againstand become interlockingly embedded in an annular block or insulator 60of polytetrafiuoroethylene or other suitable dielectric plasticmaterial, this insulator block constituting a support for the centerconductor assembly of the termination, as well appear. Rubber 0-ring 59of circular section is received in an annular groove formed in theexternal cylindrical surface of the insulator block 69 and engages theinternal surface of the connector tube 50 in the provision of a fluidtight seal. A number of axially elongated circumferentially spacedopenings or slots 61 are formed in that portion of the connector tube 50which lies between the circular section body 45 of the termination andthe annular insulating block 60, these apertures placing the interiorchamber of the connector tube in communication with an upper annularcasing chamber 6 2 which is above the circular body 45 and incommunication with the heat exchanger receptacle R through theconnecting tube 22.

The lower end of the ceramic tube 41 is embraced by the small end of theouter or horn conductor 42; the upper end of the ceramic tube isconnected to a center conductor connector 64 within and coaxial to theconnector tube 50. The metal center conductor 64, which is of circularsection, is formed at its lower end, which is the same diameter as theceramic tube 41, with an internal thin walled cylindrical socket 65 thatreceives reduced diameter upper end portion 66 of the ceramic tube 41,the latter being preliminarily turned or ground down to the desireddiameter and coated with silver or other conductive metal paint orplated with copper to provide a terminal band 67 Which extends onto andmakes annular electrical connection with the end portion of thedeposited carbon film coating. The joint is preferably soldered.

High frequency electrical energy from a signal generator such as atelevision transmitter or other source, which energy is to be absorbedand converted into heat by the termination T, is conducted to thetermination over inner and outer conductors 71 and 72 of a suitablecoaxial transmission line, indicated diagrammatically in FIG. 1. Thecoaxial transmission line, conventional in character, is provided withterminal fittings by means of which the inner and outer conductors 71and 72 are respectively connected to inner terminal 73 and the portionof the connector tube 50 which projects through the top 10 of the casingand constitutes the connector terminal for the outer conductor of thetermination T.

The inner terminal 73 is of circular cross section and desirably maycomprise a turning of brass or similar metal formed at its upper endwith a cylindrical cup 74 which is adapted to receive a connector plugof the quick disconnect fitting (not shown) on the coaxial transmissionline. This terminal is formed with a reduced diameter shank portion 75that extends axially and downwardly through center opening or bore 76 inthe insulator 60, the reduction in diameter from the outer projectingportion of the terminal 73 which contains the terminal socket 74 to thediameter of the shank portion 75 compensates for the difference in thedielectric constant of the air in which the socket portion of theterminal is located and the polytetrafiuoroethylene or other insulatingmaterial in which the shank portion 75 is located, thereby maintainingsubstantially the same characteristic im pedance axially along thelength of the device.

A strong frictional grip may be obtained between the walls 74 of theterminal cup and the center terminal plug of a coaxial line fittingattached to the present de vice. Accordingly, unless provision is madefor a strong grip between and anchorage of the internal parts of thepresent device, the center cenductor structure or assembly, includingthe center connector 64 and the ceramic tube 41 which carries theresistive film 4b, is likely to be objectionably disturbed or shiftedaxially when the transmission line is uncoupled. By reason of therelatively greater area of contact between the connector tube 56 and theoutside of the insulator on as compared to the inside bore of theinsulator and the outside of the center terminal elements 73, slippingand shifting normally are more likely to be encountered between thelatter parts. Thus, special provision is made in the form of an expandedand interlocked structure for anchorage of the inner terminal elementwithin the surrounding insulator. The shank 75 of the terminal element73 is expanded radially outwardly against the walls of the bore 76 inthe solid insulator 60 and an interlock established. The insulator is inturn circumferentially embraced by the cylindrical walls of theconnector tube Sit and thus capable of strongly resisting the expansionof the terminal element shank 75 to maintain a lasting permanent grip ofone part on another. To distend the shank 75 a pluglike expander 8%(FIG. 7) is forced axially through a center bore in the terminalelement, the expander having a tapered end 81 which engages an internalshoulder or shoulders 82 formed at the juncture of axial inner bore 83and an outer threaded counterbore 84 which extends into the terminalelement through the bottom of the cylindrical cup 74. Other types ofexpanders may, of course, be employed and the expander may be variouslyforced into place, a preferred arrangement being the use of the internalthreads in the counterbore 84 of the terminal element 73 which cooperatewith external threads 85 on the expander 80 to shift the expanderaxially relative to the terminal element upon relative turning so as toforce the tapered end 81 against the shoulder 82. The expander is turnedas by a hex or other noncircular tool or instrument, indicated at 86,inserted temporarily and for the purpose axially through the cup 74 andinto a matching socket in the expander 80.

As a further refinement of the structural combination that holds thecenter conductor assembly or structure in place the terminal elementshank 75 is formed with axial slots 87 which extend through the shoulder82 in the provision of a number of tines or fingers 88. The shoulder 82thus comprises a circumferential series of arcuate shoulders concentricto the axis of the terminal element and spaced axially from both ends ofthe slots. At its end opposite the terminal cup 74 the element 73 isformed with a reduced diameter end portion 89 receivable in matchingsocket 90 of intermediate element 91 that has a telescoping connectionwith the center conductor connector 64. The embracement of the ends ofthe tines 88 by the walls of the socket 9t) prevents expansion of thelower end of the slotted shank 75 under the radial pressure of theexpander 89 so that the expansion of the terminal element takes the formof an outward or radial bowing of each of the tines or fingers 88, withthe maximum radial distention occurring in the region of the shoulder orshoulders 82 engaged directly by the tapered end 81 of the expander. Therelative movements of the parts such as the expander and the tines ofthe terminal element in such expansion may be small dimensionally and,in fact, are not shown in the drawings, the relatively stiff plasticblock 60 strongly resisting distortion. Rubber O-ring 93 is received inan annular recessed groove formed in the wall of the bore 76 in theplastic insulator and engages the cylindrical external surface of theintermediate element 91 to seal the bore 76.

The insulator 60, which, as previously mentioned, is preferably arelatively stiff plastic material such as polytetrafiuoroethylene, whileincompressible, or substantially so, is sutficiently deformable so thatunder the expanding pressures exerted by the bowed tines 88 it tends tofiow slightly into the slots 87, thereby providing an interlockmechanical in nature between the terminal element 73 and the insulatorwhich resists turning of the terminal element relative to the insulator.The outward bowing of the tines 88, which may of course result in slightaxial swelling of the plastic insulator 6%, also provides an interlockmechanical in nature between the terminal element 73 and the insulatorwhich resists relative axial shifting of the parts. Thus inner terminalelement 73 is both frictionally gripped and mechanically interlocked byand with the surrounding annular plastic insulator 60 in such a manneras effectively to prevent both relative turning and objectionable axialdisplacement or shifting of the center conductor structure of the deviceunder such forces as are encountered in normal use or incidental toconnecting and disconnecting a coaxial transmission line.

Besides effecting a strong grip and interlock between the insulator andthe terminal element 73 by expansion of the latter, the expandingpressure is transmitted radially through the walls of the insulator 60to the embracing cylindrical walls of the connector tube 50, which thusmaintains a tight grip on the insulator to resist relative turning andaxial shifting of the parts. To further insure against axial shiftingand turning of the insulator in the connector tube 50 an interlock isprovided in the form of the radial set screws 56 threaded throughaligned openings in the connector tube 50 and in the surrounding ring54, the openings being suitably tapped to receive the set screws. Asshown in FIG. 6, the set screws bite into the periphery of the insulator60.

At the small end of the termination the tapered outer conductor 42 maybe curved into tangential contact with the deposited resistive filmcoating 40 of the center conductor or, and this is the preferredarrangement, may include a relatively short integral cylindrical endsection or portion 95 to provide an annular radially shallow clearancespace 96 of uniform circular section surrounding the resistive film 40of the center conductor. This annular clearance is more effective forthe flow of liquid coolant than the tapered clearance space resultingfrom tangential contact between the curved horn and the cylindrical filmresistor, as called for by theoretical considerations governing thedesign of reflectionless terminations for coaxial lines. To compensatefor the departure from such theoretical considerations resulting fromuse of the cylindrical end section 95, a capacitance compensatinginductive metal tube 102 is disposed inside the end of the resistiveconductor tube 41 and electrically connected to the small end of theconductor horn 42.

Contact is made between the horn conductor 42 and the resistive innerconductor 40 by a reduced diameter cylindrical end 97 which is integralwith and extends as an axial continuation or extension of thecylindrical portion 95. The small cylindrical end portion or section 95of the horn conductor 42 is formed with apertures such as axiallyelongated slots 93 for admitting liquid coolant to the dielectric spacebetween the termination conductors, as will be described later. Theseslots extend the full length of the cylindrical portion 95 and arespaced uniformly about the circumference of such cylindrical portion. Atleast one of the slots 93 is continuous through the reduced diametercylindrical end portion 97, as indicated at 123, FIG. 9; to permitexpansion and contraction of the latter in yieldingly gripping the endof the inner conductor. Electrical connection may be made directlybetween the carbon film coating 40, comprising the inner conductor, andthe cylindrically curved inner surface of the extreme end or terminalportion 97 of the metal horn conductor 42. Suitable yielding clampingmeans such as a plurality of axially spaced parallel split spring rings99 is provided to contract resiliently about the cylindrical end portion97. The cylindrical terminal end of the horn conductor is thus held orcompressed conformatively against the inner conductor for goodelectrical contact with the latter.

A preferred arrangement for connecting the compensating tube 102 to thehorn 42 is described in copending application Serial No. 798,728 filedMarch 11, 1959. According to such arrangement a conductive metal band100 in the form of a strip of thin sheet brass is wrapped about the endportion of the carbon film 40 on the ceramic tube 41 and permanentlysecured by solder 94. The solder bonds to a conductive film or bandcoating 1195 of copper electroplated on the end portion of the carbonfilm. The brass terminal band 100 extends axially beyond the end of theceramic tube 41 and embraces a brass ring 101 located against the end ofthe ceramic tube. The ring 161 is soldered to the metal terminal elementor band 1% and at 113 to the brass tube 102 which is telescoped withinthe end of the ceramic tube 41.

The metal capacitance compensating tube 102 is of such length that itsupper or innermost end 1113 is disposed approximately at the radialplane defined by the juncture indicated at 109 between the cylindricalend portion 95 and the tapered portion of the outer horn conductor 42.Capacitance between the conductive metal sleeve 1% and the filmconductor 40 compensates for loss in capacitive coupling between thetapered horn conductor 4' 2 and the resistive film conductor 40resulting from using the cylindrical portion 95 at the small end of thehorn conductor instead of continuing the curvature of the tapered horninto tangential contact with the cylindrical surface of the resistivefilm conductor as called for by the theoretical considerationspreviously referred to which govern the design of refiectionlessterminations.

The termination T is aligned axially with the entrant tube 28 throughwhich the circulating liquid dielectric coolant is introduced into thecasing C, the inflowing liquid being thus directed to flow axiallyagainst the small end of the termination. To guide and confine the fiowof the liquid a funnel 106 embraces both the ends of the termination andinlet end 1117 of the entrant tube 28. The funnel has a stem portion 103received about the small end of the horn conductor 42, the funnel stembeing soldered to and making substantially annular sealing contact withthe external surface of the horn conductor at a circular line 104 aboveor spaced toward the large end of the termination from upper ends of theaxial slots 98 and 116 which admit the liquid dielectric coolant intoannular space 6 between the horn conductor and the inner resistive filmconductor 41?. The interior of the cylindrical stern portion 108 of thefunnel is of larger diameter than that portion of the external surfaceof the horn conductor 42 surrounded thereby to define annular clearancespace 110 extending the full length of the axial conductor slots 98 and116. This space provides a passage for axial flow of entering liquidcoolant in the form of a tubular sheath so that such coolant may enterthe annular dielectric space 96 along the full length of each of theslots 98 and 116.

At its other or lower end the funnel 106 is formed with a bell end 111which surrounds the end 1ti7 of the entrant tube 28 in embracing butslightly spaced relation, the annular clearance thus provided beingindicated at 112. The bell end 111 is formed with a flared lip 114 whichacts as a pilot to guide the funnel over the tube end 107 in assemblingthe parts into the telescoped relation shown. The infiowing liquid isconfined by the entrant funnel 106 and constrained to fiow into theannular dielectric space between the resistive inner film conductor 40and the tapered outer conductor 12 at the small end of the termination.

The liquid dielectric coolant surrounding the tapered outer or hornconductor 42 is in a quiescent state, or substantially so, the flowthrough lower outer portion 115 of the casing chamber being relativelysmall or nonexistent and resulting from permissible leakage between thebody 45 of the termination and the casing walls for reinforcing ring 47.

Equalization of pressure between the interior or dielectric space of thetermination and the outer casing chamber 115 is obtained through theannular clearance 112 between the funnel 106 and the end 107 of the tube28.

In circulation of the liquid dielectric coolant about its circuit theflow through the casing C is confined substantially to the annulardielectric space separating the inner and outer conductors of thetermination. The termination body 45 constitutes, in effect, a partitionor barrier across the path of the circulating liquid and the liquidentrance and exit openings of the casing are located near correspondingentrance and exit slots 98, 116 and 61 in the outer conductor of thetermination to constrain the flow of the coolant within the casingsubstantially to the annular dielectric space between the coaxialconductors of the termination.

The liquid dielectric coolant is desirably maintained in a path closelysurrounding the resistive inner film conductor 40 as by a tubular guide118 which surrounds the inner conductor. The guide tube 118 is formed ofa suitable dielectric material such as a plastic or, as here shown, ofglass.

At its end adjacent to the small end of the termination T the glassguide 118 is telescoped into collar 120 of plastic dielectric materialformed with a tapered external surface which fits the internal taperedcontour of the outer conductor 4-2. An opening or passage 122 throughthe wall of the collar 120 permits pressure equalizing flow of thecoolant.

At its other or upper end the tubular glass guide 118 is formed with anintegral flared end 125 received in a locating and sealing ring 127formed of suitable plastic material.

To insure a small fluid flow through the chamber 124 that surrounds theguide 118 the sealing ring 127 is formed with an axial passage 128 whichthus connects the chamber portion 124 with the space between the centerconductor connector 64 and the connector tube 51 The passage 128 in theplastic ring 127 and the passage 122 in the plastic collar or thimble121) are respectively located substantially at the extreme upper andextreme lower ends of the chamber portion 124 to result in a limitedflow of liquid dielectric coolant through such apertures or openingsinto and out of the tapered portion of the dielectric space of thetermination that has a scavenging effect which carries occluded air orother gas. The annular dielectric block 611 sealing the upper end of theconnector tube 5d extends downwardly at least to the tops (as shown) oreven below the upper ends of the slots 61 and also below the top of theport or opening in the pipe or tube 22 through which the coolant isdischarged from the casing C into the receptacle R to prevent entrapmentof air or gas in the dielectric space at the upper end of thetermination.

The maximum diameters and cross sectional areas of the guide tube 118and of the plastic sealing rings 12% and 127 are each less than thediameter and cross sectional area of the interior opening or passage ofthe connector tube St} so that in assembling the guide tube 118, collaror thimble 1211 and the sealing ring 127 into the outer conductorstructure of the termination, the guide tube may be inserted axiallyinto place through the open terminal end of the connector tube 50 priorto insertion therein of the annular insulator block 60 and the innerconductor assembly. In commercial PllO- duction of the device thecircular body 45, the connector tube 50 and the tapered horn conductor42 are conveniently assembled together in the telescoped relation shownwhile outside of the casing body tube 1. The guide tube 118 is alsomoved into place prior to assembly into the line of the inner conductorcomponents and while the outer conductor components are outside thecasing tube 1. The annular insulator block 60 is assembled about theinner terminal element 73 by sliding it axially over the inner conductor41 to the desired location about the shank 75 of the inner terminalelement 73, the block being axially located in such assembly by aplastic dielectric washer 13! interposed between the block and theshoulder provided by the relatively large diameter head end of the innerterminal element 73. The center conductor structure of the termination,comprising the ceramic tube 4-1 with its terminal band 100, thecapacitance compensating tube 1&2, the connector 64, the terminal 73,and the dielectric insulating block 66, is then assembled with the outerconductor structure by relative axial telescoping movement to theposition shown in FIGS. 2, 4, and 9. The top closure 10, including thering 54, is placed about the connector tube Sti, secured as by brazingor welding and the holes for the set screws 56 drilled and tapped in apreliminary sub-assembly procedure.

Prior to the insertion of the termination T or the outer conductor 42thereof into the casing C the funnel element 1% is assembled onto thesmall end of the outer conductor by telescoping such element into placeand soldering or razing the end of the stem portion 1% to the externalsurface of the outer conductor 42. The spring clamping rings 99 areassembled about the axially split cylindrical end 97 of the outerconductor either before or after the inner conductor structure has beenmoved into place. The clamping force of the split conductor end 97 aboutthe terminal band 1% on the inner conductor is insufficient to preventaxial adjusting movement of the inner conductor structure relative tothe outer conductor structure. In telescopically assembling the tubularguide 118 and the inner conductor structure with the outer conductorstructure prior to the insertion of the later into the casing body 1,the parts may be easily and accurately placed by telescopic movement indesired predetermined relative axial positions, as by means of suitableassembly jigs. In such initial assembly outside the casing C the setscrews 52 and 56 may also be advanced or adjusted into engagement withthe plastic sealing ring 127 of the guide tube 118 and with the annulardielectric block 60 to secure these plastic components in place. Thusthe termination T, including the inner and outer conductor assemblies,the guide tube 118, and with the casing tube closure attached to theconnector tube 543, is insertable by axial movement as a unit into thecasing C, the engagement between the upper rim of the casing body tube 1and the periphery of the top closure 10 serving to locate the lineassembly in the casing. During the movement into position of theinsertable line unit the bell end 111 of the funnel element 106 servesas a pilot to guide the lower or small end of the termination T intoaxial alignment with the discharge or inlet end 107 of the entrant tube28, the funnel element being rigidly secured to the outer conductor 42as by the soldered joint mentioned.

The permissible axial slipping or shifting of one conductor structurerelative to the other, mentioned above, is a desirable feature not onlybecause of the accommodation of manufacturing variations which permitsgreater tolerances and the ability of the device to expand and contractdifferently upon temperature changes encountered in practice but becauseof further advantages incident to service and repair in the field. Itmay occur, for example, that one of the inner conductor components suchas the resistive film 4t? or the ceramic tube 41 becomes damaged in useor the instrument may appear to be functioning improperly so that itbecomes desirable to inspect the interior of the line or the innerconductor to determine the existence of a defect in or injury to one ofthe component parts or elements.

The structure of the present invention provides for optional removal andreplacement of the inner conductor assembly without disturbing the outerconductor assembly and without even draining or removing the liquiddielectric coolant from the casing C. To effect such removal, the maincoaxial transmission line comprising the inner and outer conductors 71and 72 previously mentioned in connection with FIG. 1 is firstdisconnected from the terminal end or" the connector tube and from thesocket or cup 74 of the inner terminal element 73 so as to disconnectthe device or instrument from the signal generator. Thereafter theinterlock and grip of the insulating block 6% on the shank 75 of theterminal element 73 is released or relieved by backing oif the expander84 which is turned relative to the terminal element by an implement suchas a hex end bar 86 inserted axially through the cup 74 of the terminalelement and into nonrotative interfitting engagement with the expander.The tines 38 being of resilient spring material such as brass, of whichthe terminal element '73 is formed, spring back to their normalunstressed shape when relieved of the expanding support provided by theexpander 30, thereby reducing the size of the terminal element shank andwithdrawing it from interlocking engagement with the walls of the bore76 in the insulator block 6 3. The interlock and grip between theinsulator block as and the terminal element shank '75 being thusreleased, the inner conductor assembly is no longer held againstrelative turning or relative axial movement of the insulating block 66and can be withdrawn bodily from within the outer conductor assembly,the inner conductor structure or assembly being lifted vertically inthis operation. The bore 7e in the insulating block 60 is, of course,slightly larger in diameter than the withdrawn parts such as theresistive coating 4% on the cylindrical ceramic tube 41 and the brassterminal band or element on the lower end of the inner conductor so thatthese parts may be withdrawn axially through the insulating block 60 inlifting the inner conductor assembly up and out through the top of theconductor tube 50 while the insulating block 69 remains permanentlyassembled and secured in the latter through the interlocking action ofthe set screws 56.

Upon replacement of the same or a duplicate substitute inner conductorassembly the brass terminal band 100 bears the frictional load imposedby the split clamping end 97 of the horn conductor which, under theresilient squeezing action of the spring rings 99 and by reason of theinherent resilience of the brass or other metal stock from which thehorn is formed, must be slightly distended by the terminal band 1% toadmit the latter in the automatic establishment of electrical connectionbetween the ends of the conductors at the remote or lower end of thetermination.

The termination T can be used to absorb the energy from a high frequencyelectrical signal generator such as a television transmitter. It may becombined with a suitable signal responsive system including a detectorconnected and arranged, say, to sample the wave signal from thetransmitter in accordance with known principles. In such an instrument apickup device or detector D, like the unit assembly D described inapplication Serial No. 99,474, filed June 16, 1949, is combined with thetermination T so that the parts function together in accordance with theprinciples described in the application referred to.

The unit D includes a chambered body member 70 of brass or similar metalformed with a cylindrical pilot extension 133 through which probe 132and plastic cap 134 project. A flat mounting plate 135 is formed with acentral aperture which receives the cylindrical extension 133 of thebody and is abutted against a shoulder of the latter, being soldered tothe body and to the cylindrical extension 133.

A circular opening 137 to receive the pilot extension 133 is formedthrough the wall of the casing 1, through the reinforcing band or ring47, and through the telescoped body 45 and connector section 44 of thetermination outer conductor. This opening through the juxtaposed partsis of such size as to provide a sliding fit with the pilot extension 133received therein, the pilot thus keying the parts together. RubberO-ring 136 is received in a circular groove formed in the externalcylindrical surface of the extension 133. A flat spot face 138 on theoutside of the casing body 1 about the opening 137 receives the mountingplate 135, the latter being attached to the casing as by screws 139threaded into tapped holes that extend into the reinforcing ring 47.Reference is 13 made to copending application for patent Serial No.798,777 filed March 11, 1939, now Patent No. 2,973,479, coveringfeatures related to the interfitting of the pick-up device D with thecasing 1 and the termination T.

The present invention thus provides useful improvements in specializedapparatus for converting high frequency electrical energy into heat anddissipating such energy.

In accordance with the patent statutes the principles of the presentinvention may be utilized in various ways, numerous modifications andalterations being contemplated, substitution of parts and changes inconstruction being resorted to as desired, it being understood that theembodiment shown in the drawings and described above is given merely forpurposes of explanation and illustration without intending to limit thescope of the claims to the specific details disclosed.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

1. A'high frequency electrical line terminating device comprising anelongated tubular casing open at one end, a coaxial line sectioncomprising an inner conductor and an outer conductor surrounding theinner conductor in spaced relation, a closure disposed across said openend of the casing, one end of the line section projecting through theclosure and having inner and outer terminals for connection to the innerand outer conductors of a coaxial transmission line, means detachablysecuring the closure to the casing for facile removal and replacement ofthe closure and the line section from and into predetermined position inthe casing as a unit, conduit means connected to the casing forsupplying and withdrawing liquid coolant, said conduit means having anentrant element at the other end of the casing, means carried by theline section registered with the entrant element to receive liquidcoolant from such element and conduct the received coolant directly tothe space between the conductors, said liquid receiving means being fastto the line section and readily separatable from the entrant element forremoval with the line section, and the liquid receiving means and theentrant element automatically registering upon replacement of the linesection to said predetermined position.

2. A terminating device as in claim 1 in which the entrant elementcomprises a tube projecting into the interior of the casing and theliquid receiving means comprises a tube disposed in interfittingrelation with the entrant tube, said tubes being readily separable byrelative axial movement in one direction for removal of the line sectionand being readily interfittable by relative axial movement in thereverse direction for replacement of the line section.

3. In a high frequency electrical device of the character described, aline section comprising an inner conductor and a tubular outer conductorarranged coaxially with an annular dielectric space surrounding theinner conductor, an expandable insulator having a central opening with awall of circular section closely embracing the inner conductor, saidinsulator extending radially outwardly from the inner conductor intoengagement with the outer conductor to locate and support the innerconductor in fixed relation to the outer conductor, said inner conductorincluding axially spaced end portions and a central holding portionbetween such end portions, the central holding portion being locatedwholly between and spaced toward the center from the axial limits of theinsulator and readily expandable radially relative to the end portions,said holding portion of the inner conductor comprising a plurality ofaxially elongated conductive elements of resilient spring materialdisposed in symmetric relation about and equally spaced from the axis ofthe line section, said elements being fast to and mechanically andelectrically connecting the end portions and in engagement with theinsulator wall, an expander supported within the inner conductor andadapted to be actuated for coaction with the inner conductor forrelative axial shifting,

said expander upon actuation in one direction being adapted to bearradially outwardly against the elongated elements upon such axialshifting to thereby expand the central portion of the inner conductorand force the elements strongly against the insulator wall and theinsulator against the tubular outer conductor in the establishment ofstrong frictional grips between the insulator and the conductors forholding the conductors in fixed relation, and, upon actuation of theexpander in a reverse direction, the inherent resiliency of the springelements being adapted to contract the central portion of the innerconductor to thereby release the insulator and the conductors.

4. In a high frequency device as in claim 3 the inner conductor beingformed with a threaded axial bore, the expander being threaded into thebore and located wholly between the axial limits of the inner conductor,and the inner conductor having an axial passage adapted to admit a toolfor engagement with the expander to turn the latter in effecting saidaxial shifting.

5. In a high frequency device as in claim 3 one of the end portions ofthe inner conductor having a cylindrical surface located axially beyondthe elongated elements, the insulator having a cylindrical surfaceportion surrounding said cylindrical surface of the inner conductor, anda resilient deformable sealing ring recessed into said cylindricalsurface of the insulator and closely embracing the inner conductor insealing relation.

6. In a high frequency device as in claim 3 the tubular outer conductorand one of the end portions of the inner conductor having cylindricalsurfaces, the insulator having cylindrical surface portions onesurrounding the cylindrical surface of said one end portion of the innerconductor, another surrounded by the cylindrical surface of the outerconductor, and resilient deformable sealing rings recessed into thecylindrical portions of the insulator and sealingly engaging theconductors.

7. In a high frequency electrical device of the character described inwhich an inner conductor and an outer conductor are arranged as acoaxial line and in which an annular insulator surrounds the innerconductor to 10- cate and support the latter in the outer conductor, animproved inner conductor structure comprising an elongated tubularmember having a central portion embraced by the annular insulator andformed with axial slots for radial expansion, said slotted centralportion termination at both of its opposite extremities short of theaxial limits of the insulator, the inner conductor having end portionsmechanically and electrically connected to the extremities of theslotted central portion and restraining said extremities against radialexpansion, an expander receivable within the tubular member, theexpander and the tubular member being formed with means and the expanderbeing adapted for actuation to coact with the tubular member to effectrelative longitudinal adjusting movement of the expander and to retainthe expander in adjustment, the tubular member having an internalformation and the expander having an external formation adapted tocooperate to effect expansion of the tubular member against theinsulator upon relative axial movement therein of the expander, andmeans on the opposite ends of the tubular member for connecting suchtubular member to inner conductor components of the line in coaxialrelation thereto, one of said connecting means being formed with anaxial aperture through which to insert an implement for engaging theexpander to effect axial movement of the latter relative to the tubularmember.

8. A high frequency electrical device comprising a casing adapted tocontain a body of liquid dielectric coolant and having a top accessopening, a coaxial line section disposed within the casing so as to beimmersed in such a liquid body, the line section comprising an innerconductor and an outer conductor surrounding the inner conductor inspaced relation, a closure disposed across the access opening and formedwith a central aperture, the line section including inner and outerterminals separated by an annular dielectric space, said terminals beingelectrically connected to the inner and outer conductors, respectively,and projecting upwardly through the aperture in the closure, the outerterminal being secured to the closure to support the line sectiontherefrom, an insulator filling the space between the terminals andthereby preventing loss of dielectric liquid out the aperture in theclosure through such space, means interlocking the insulator and theouter terminal preventing axial movement of the insulator relative tothe outer terminal, said insulator having a central through opening inwhich is received the inner terminal, the inner conductor comprising anelongated resistive member electrically connected at one end to theinner terminal and, at its other end, having a terminal band, the outerconductor comprising an elongated tubular member electrically connectedat one end to the outer terminal and, at its other end, having aradially yieldable terminal portion resiliently embracing the terminalband in the provision of an electrical connection between the conductorswhich permits relative longitudinal shifting of the conductors, theinner conductor throughout its length from the insulator to andincluding the terminal band being receivable through the insulatoropening to permit vertical axial withdrawal and reinsertion of the innerconductor from and into the casing and the outer conductor with theliquid dielectric body remaining in the latter and while the outerconductor and the closure remain in place, the terminal portion of theouter conductor being adapted automatically to re-establish electricalconnection with the terminal band of the inner conductor uponreinsertion of the latter, the closure together with the inner and outerterminals and the inner and outer conductors fast together as a unitbeing axially removable from and replaceable on and into the casing withthe liquid dielectric body remaining in the latter.

9. A device as in claim 8 having means actuatable to lock the innerterminal in the insulator and prevent axial movement of such innerterminal relative to the insulator.

10. \A device as in claim 8 in which the outer conductor a is taperedtoward its terminal portion and guides the end of the inner conductorhaving the terminal band into predetermined coaxial relation during saidreinsertion.

11. In a high frequency electrical device of the character described aninner conductor and an outer conductor arranged coaxially, the innerconductor comprising an elongated relatively resistive member having asubstantially cylindrical terminal on one end and on the other end anaxially extending connector, the other conductor comprising an elongatedtubular member surrounding the inner conductor in generally spacedrelation and at one end having a terminal portion closely andy-ieldingly embracing the terminal end of the inner conductor to effectelectrical conection therewith while permitting relative axial slidingof the terminal end within said terminal portion, an insulator in thespace between the conductors and spaced axially from the terminal endand the terminal portion to locate the inner conductor in coaxialrelation to the outer conductor, the inner conductor being insertableinto the outer conductor and withdrawable therefrom through theinsulator by endwise movement, and means for releasably securing theconnector of the inner conductor in the insulator to resist withdrawalof the inner conductor.

12. In a high frequency electrical device comprising a casing having anopening and, projecting into the casing through such opening, a coaxialline section, the line section comprising a tubular outer conductor andan inner conductor extending through the outer conductor in spacedcoaxial relation, a plastic insulator surrounding the inner conductor insupporting relation and extending radially outwardly from the innerconductor into engagement with the outer conductor, said outer conductorcomprising a relatively thin metal tube in sur rounding contact with theinsulator and a body of relatively thick section encircling the tube andcomprising a closure member extending radially beyond the thin metaltube, the closure member at its outer periphery being detachably securedto the casing for removal and replacement of the closure member and theline section as a unit, and a locking element extending radially throughboth the thick body and the thin tube and having an inner and embeddedin the plastic insulator.

13. In a line section as in claim 12 the outer conductor being formedwith a tapped radial bore and the locking element comprising a set screwthreaded into such bore.

14. A high frequency electrical line terminating device comprising incombination an elongated hollow casing having an access opening in oneend, a coaxial line section having an inside end within and an outsideend without the casing, said line section comprising an elongated innerconductor and a tubular outer conductor, the outer conductor surroundingthe inner conductor in spaced coaxial relation and including a member ofcircular section tapered from a large diameter end to a small diameterend, said small end embracing and being electrically connected to oneend of the inner conductor at the inside end of the line section, theouter conductor including a body member at the large end of the taperedmember, said body member being relatively short axially and locatedintermediate and spaced from the ends of the line section, said bodymember being axially slidable relative to and, at a point spaced axiallyfrom said end opening, closely embraced by the casing to locate the linesection in predetermined relation to the casing, the outer conductorincluding a connector tube having a portion extending into the casingwith one end fast to one side of the body member, said connector tubeportion being surrounded by an annular clearance space separating theconnector tube from the casing, the inner conductor extending axiallythrough the body member and the connector tube and having on its outerend a terminal for connection to the inner conductor of a coaxialtransmission line, a closure disposed across said end opening, theconnector tube projecting through and being fast to the closure and atsaid outside end having a terminal for connection to the outer conductorof a coaxial transmission line, said tapered member at its large endbeing fast to the other side of the body member and projecting axiallytherefrom cantilever fashion and in coaxial relation into the interiorof the casing, the tapered member being wholly supported from and by thebody member, means securing the closure to the casing for faciledisconnection and reconnection, the closure together with the linesection as a unit being adapted for easy axial removal from the casingupon such disconnection and for easy axial replacement, and locatingmeans on the closure and on the casing adapted to bear one against theother automatically to limit relative axial movement of the line sectioninto the casing and thereby position the line section in predeterminedaxial relation to the casing in such replacement.

15. A device as defined in claim 14 in which the casing is of uniformsection and has a cylindrical internal surface, the closure has aninside locating portion received within the casing and peripherallyengaged against such cylindrical surface, and the locating means on theclosure comprises a radial flange portion adapted to bear axiallyagainst the casing.

16. A high frequency electrical line terminating device comprising incombination an elongated hollow casing having an access opening in oneend, a coaxial line section having an inside end within and an outsideend without the casing, said line section comprising an elongated innerconductor and a tubular outer conductor, the outer con ductorsurrounding the inner conductor in spaced coaxial relation and includinga member of circular section tapered from a large diameter end to asmall diameter end, said small end embracing and being electricallyconnected to one end of the inner conductor at the inside end of theline section, the outer conductor including a body member at the largeend of the tapered member, said body member being relatively shortaxially and located intermediate and spaced from the ends of the linesection, said body member being axially slidable relative to and, at apoint spaced axially from said end opening, closely embraced by thecasing to locate the line section in predetermined relation to thecasing, a closure disposed across said end opening, the line sectionprojecting through and being first to the closure and at said outsideend having inner and outer terminals for connection to the inner andouter conductors of a coaxial transmission line, said tapered member atits large end being fast to the body member and projecting axiallytherefrom cantilever fashion and in coaxial relation into the interiorof the casing, the tapered member being wholly supported from and by thebody member, the closure together with the line section as a unit beingadapted for easy axial removal from and replacement in the casing, meansfor supplying liquid coolant including an entrant tube connected to andhaving a discharge opening into the casing, said line section alsoincluding liquid conducting means having an internal passage continuouswith the space between the conductors, said conducting means having areceiving opening into the passage, and said eating of the line sectionalso serving to register the receiving opening of the line sectionliquid conducting means with the discharge opening of the entrant tubeduring such replacement.

17. A device as defined in claim 16 in which the entrant tube has aninner end formed with said discharge opening and projecting into theinterior of the casing and the liquid conducting means is telescopicallyinterfitted With said inner end of the entrant tube.

18. In a high frequency electrical device of the character describedcomprising an elongated inner conductor and an elongated tubular outerconductor arranged as a coaxial line and separated by a dielectricspace, an annular one piece insulator in said space surrounding theinner conductor and supporting the latter in the outer conductor, theinner conductor having an axial bore and including means located whollyintermediate and spaced axially from both ends of the one pieceinsulator expandable radially to lock the inner conductor and theinsulator together against relative axial shifting, an expander of lessaxial length than the inner conductor dis- 18 posed in the bore andguided therein for relative axial shifting, and threaded meansactuatable to effect such axial shifting of the guided expander in thebore, the expander being adapted upon such shifting to expand saidexpandable means and effect locking together of the inner conductor andthe insulator.

19. In an electrical device as claimed in claim 18 the threaded meanscomprising mating threads formed in the inner conductor and on theexpander, and said shifting of the expander being effected by and uponrotation of the expander within the inner conductor.

20. In an electrical device as claimed in claim 18, the conductorshaving at one end of the line means for connecting them to terminalfittings on the conductors of a coaxial transmission line, the inner andtubular outer conductors at their other ends comprising elements of anattenuating line section, the latter elements being retained inpredetermined positions relative to one another by said locking togetherin resisting forces tending to shift one such element axially relativeto the other resulting from axial loads imposed on the inner and outerconductors at said one end of the line in connecting and disconnecting atransmission line.

21. In an electrical device as claimed in claim 20, the attenuating linesection element of the inner conductor being withdrawable axially fromthe outer conductor and through the insulator upon contraction of saidexpandable means and unlocking of the inner conductor and the insulator.

References fitted in the file of this patent UNITED STATES PATENTS1,981,753 Pearson Nov. 20, 1934 2,057,242 Mautsch Oct. 13, 19362,395,196 Roberds Feb. 19, 1946 2,399,930 Keister May 7, 1946 2,453,283Tiley et al Nov. 9, 1948 2,551,611 Kuhner May 8, 1951 2,552,707 Bird eta1 May 15, 1951 2,556,642 Bird June 12, 1951 2,663,753 Bird Dec. 22,1953 2,752,572 Bird et a1 June 26, 1956 FOREIGN PATENTS 617,699 GreatBritain Feb. 10, 1949

